Cholinergic mechanisms play an important role in the physiology of the primate anterior ocular segment, as well as in treatment of glaucoma. The studies proposed are designed to increase our understanding of the basic cholinergic pharmacology of the ciliary muscle by investigating in vitro the contractile responses of this muscle obtained from cynomolgus monkeys. These in vitro studies will provide information that is novel and that is not obtainable from studies in vivo. Specifically, these studies will: a. define the potencies and affinities for a number of cholinergic agonists in the ciliary muscle b. define the pA2 for a number of muscarinic antagonists in this system c. determine whether or not the ciliary muscle is a "spare receptor" system d. determine whether there are multiple muscarinic subtypes in the ciliary muscle e. determine whether receptor binding is modulated by guanine nucleotides In vivo studies in this proposal will establish a dose response relationship for aceclidine, a cholinergic agonist that reportedly lowers intraocular pressure with minimal effects on accommodation. These studies should improve our understanding of the role of cholinergic mechanisms when autonomic drugs are used to reduce the intraocular pressure in treatment of open-angle glaucoma.